The present invention relates generally to memory cards and, more particularly, to a memory card (e.g., a multi-media card (MMC)) which is configured such that the host socket connector pins travel only over the metallic contacts of the memory card and not any mold compound thereof, thus substantially enhancing the durability of the host socket connector pins.
As is well known in the electronics industry, memory cards are being used in increasing numbers to provide memory storage and other electronic functions for devices such as digital cameras, MP3 players, cellular phones, and personal digital assistants. In this regard, memory cards are provided in various formats, including multi-media cards and secure digital cards.
Typically, memory cards comprise multiple integrated circuit devices or semiconductor dies. The dies are interconnected using a circuit board substrate which adds to the weight, thickness, stiffness and complexity of the card. Memory cards also include electrical contacts for providing an external interface to an insertion point or socket. These electrical contacts are typically disposed on the back side of the circuit board substrate, with the electrical connection to the dies being provided by vias which extend through the circuit board substrate.
In an effort to simplify the process steps needed to fabricate the memory card, there has been developed by Applicant a memory card wherein a leadframe assembly is used as an alternative to the circuit board substrate, as described in Applicant's co-pending U.S. application Ser. No. 09/956,190 entitled LEAD-FRAME METHOD AND ASSEMBLY FOR INTERCONNECTING CIRCUITS WITHIN A CIRCUIT MODULE filed Sep. 19, 2001, of which the present application is a continuation-in-part. As is described in Ser. No. 09/956,190, the leadframe and semiconductor die of the memory card are covered with an encapsulant which hardens into a cover or body of the memory card. The body is sized and configured to meet or achieve a “form factor” for the memory card. In the completed memory card, the contacts of the leadframe are exposed within a common surface of the body, with a die pad of the leadframe and the semiconductor die mounted thereto being disposed within or covered by the body.
Applicant has previously determined that the molding or encapsulation process used to form the body of the card sometimes gives rise to structural deficiencies or problems within the resultant memory card. These problems include portions of the die pad of the leadframe being exposed in the body of the memory card, flash being disposed on the contacts of the leadframe, chipping in a peripheral flange area of the body, and mold gate pull-out wherein a portion of the mold or encapsulating compound is pulled out from within the body, leaving a small recess or void therein. To address these particular problems, Applicant has previously developed a memory card having a “die down” configuration attributable to the structural attributes of the leadframe included therein, and an associated molding methodology employed in the fabrication of such memory card. This die-down memory card is disclosed in Applicant's co-pending U.S. application Ser. No. 10/266,329 entitled DIE DOWN MULTI-MEDIA CARD AND METHOD OF MAKING SAME filed Oct. 8, 2002, the disclosure of which is also incorporated herein by reference.
Memory cards, such as multi-media cards, are used by advancing the same into a host socket which includes a plurality of connector pins. Many host sockets include nine connector pins to accommodate the seven contacts included in many memory card formats such as multi-media cards, and the nine contacts included in the secure digital card memory card format. In current memory cards, the bottom surfaces of the contacts are exposed in and substantially flush with the bottom surface of the body of the memory card. A relatively narrow rail or segment of the body extends between and thus separates the contacts from the lateral side of the body which is advanced into the host socket. As a result, the connector pins of the host socket must travel over this rail or segment of the mold compound of the body prior to engaging the exposed bottom surfaces of the contacts of the memory card. The travel or rubbing of the connector pins on the mold compound tends to rapidly wear out the connector pins, especially when the mold compound contains high levels of filler material. As a result, the host socket connector pins are unable to survive the typical mating insertion requirement of ten thousand insertion cycles.
The present invention addresses and overcomes the above-described deficiencies of currently known memory cards by providing a memory card which is specifically configured to eliminate the travel of the host socket connector pins over the mold compound of the body of the memory card. More particularly, the memory card of the present invention includes a leadframe which has an external signal contact (ESC) feature which is placed to prevent damage to the host socket connector pins or contacts during memory card insertion into the host socket. These and other attributes of the present invention will be described in more detail below.